1. Field of the Invention
The present invention relates to an exhaust gas purification catalyst, a method of producing the same, and an exhaust gas purification method using the same.
2. Description of Related Art
In the related art, various kinds of exhaust gas purification catalysts have been studied in order to purify harmful components (for example, carbon monoxide (CO) and hydrocarbon (HC)) in gas exhausted from an internal combustion engine such as a diesel engine or a lean burn engine having low specific fuel consumption. As such an exhaust gas purification catalyst, an exhaust gas purification catalyst using various metal oxides as a support has been proposed.
As such an exhaust gas purification catalyst, for example, Japanese Patent Application Publication No. 2007-697 (JP-2007-697 A) discloses an exhaust gas purification catalyst including: a support that is formed of a metal oxide such as alumina; noble metal particles of Pt, Pd, Rh, or the like that are supported on the insides of pores of the support; and an aggregation inhibitor that is formed of an metal oxide containing Al, Zr, Ce, and Si and with which surfaces of the noble metal particles are enclosed or coated. However, in the exhaust gas purification catalyst of the related art disclosed in JP-2007-697 A, oxidation activity to CO or HC at a low temperature is not necessarily sufficient.
In addition, Japanese Patent Application Publication No. 11-138008 (JP 11-138008 A) discloses an exhaust gas purification catalyst including: a support that is formed of a crystalline silica porous body; and a catalytic noble metal such as Pt, Rh, or Pd that is supported on the support, in which a molar ratio (SiO2/Al2O3) of silicon dioxide to aluminum oxide in the support is 1,000 or higher, the support contains 5 vol % or higher of particles having mesopores, the support has a pore distribution in which a peak value of pore sizes of the mesopores is 4.0 nm or less, and the catalytic noble metal is supported at least on the mesopores by ion exchange. Further, Japanese Patent Application Publication No. 2013-107055 (JP 2013-107055 A) discloses a catalyst support for purifying exhaust gas including: a porous body (A) that is formed of an oxide containing at least one element selected from the group consisting of Al, Ti, Zr, and Ce; and Si-based composite oxide particles (B) that are supported on the porous body (A) and contains at least one additive element selected from the group consisting of Ti, Fe, and Al, in which a specific surface area of the catalyst support after firing in air at 800° C. for 5 hours is 100 m2/g or more, and after the firing, a ratio of a pore volume of pores having a pore radius of 1 nm to 5 nm to a pore volume of pores having a pore radius of 1 nm to 100 nm is 8% to 50%. JP 2013-107055 A also discloses an exhaust gas purification catalyst including: the above-described catalyst support for purifying exhaust gas; and active metal particles (C) that are supported on the catalyst support and are formed of at least one element selected from the group consisting of Pt, Pd, Rh, Ir, Au, Ag, Cu, Co, Ni, V, Nb, Mo, and W.
However, recently, the requirements for an exhaust gas purification catalyst have increased, and an exhaust gas purification catalyst capable of exhibiting sufficient oxidation activity to carbon monoxide and hydrocarbon at a low temperature is required.